Effect of Nitrate Concentration on the Root: Shoot Ratio in Dactylis glomerata L. and on the Kinetics of Growth in the Vegetative Phase

The vegetative growth of Dactylis glomerata L. in sand was studiedunder controlled light, temperature, and nutritional conditions.Plants were daily supplied with three nutrient solutions ofdifferent nitrate concentrations (10^–2, 10^–3 and2 x 10^–4 mol I^–1). For each concentration, growthobeyed an exponential law between the fourth and seventh weeksafter sowing. The time constant of the exponential was the samefor the shoot as for the root, and showed no significant variationwith nitrate concentration. The kinetic results and the strong dependence of the root: shootratio on nitrate concentration are discussed on the basis ofThornley's model. Hypothesizing that the molecular mechanismsof nitrate absorption are independent of the nitrate concentrationof the nutrient solution, we derived a relationship betweenthe root: shoot ratio and nitrate concentration. This relationshipwas found to be compatible with the experimental results. Dactylis glomerata L., vegetative phase, kinetics of growth, root: shoot equilibrium, nitrate absorption     

Annual growth of Cassiope tetragona as a proxy for Arctic climate: developing correlative and experimental transfer functions to reconstruct past summer temperature on a millennial time scale

Annual growth of the polar evergreen shrub Cassiope tetragona on Svalbard was evaluated as a proxy for Arctic summer temperatures. Transfer functions were derived from temperature‐growth correlations of shoots and from a temperature‐growth response, obtained from experimental warming using open top chambers (OTC) in high Arctic tundra vegetation at Isdammen approximately 1.5 km southeast of Longyearbyen, Svalbard (78°N, 15 E) and in Longyeardalen, 3 km west of Isdammen from 2004 to 2006. Air temperatures, monitored throughout the summer months, were 1.3 °C higher inside the OTCs than in the control plots. Annual stem growth was measured by tagging stems and leaves, and in the lab with shoots harvested from OTCs and control plots. Annual growth parameters assessed were leaf production, sum of length and weight of individual leaves, and stem length increment derived from leaf scar distances and the distances between wintermarksepta in the stem. Wintermarksepta are formed at the end of the summer growth period when the pith is narrowing and consist of dense and dark tissue ( Fig. 1b ). The variation of annual growth in a 34‐year site chronology (based on Cassiope shoots from the surroundings of the OTCs and control plots) correlated strongly with the mean summer temperature on Svalbard. The number of leaf pairs, leaf length and stem length also increased in the OTC warmed plots in the second and third year of warming. Transfer functions were derived from the temperature‐annual growth correlations from a single shoot from Longyeardalen, from the cross‐dated Isdammen site chronology and from the growth response to experimental warming. Based on leaf scar distances and distances between wintermarksepta of well‐preserved subfossil shoots in arctic tundra soil, annual stem length increase was assessed for the layers of a soil core collected at the Isdammen site. Based on the derived transfer functions summer temperature of the period relating to the 15 cm deep tundra soil core layer, radiocarbon dated at 4230±40 bp , may have been 3.0 °C lower than the present‐day 6.2 °C value. These results indicate that the transfer functions can be used to reconstruct past temperatures, beyond the time range of instrumental temperature and ice core records of Svalbard.

Figure 1 Open in figure viewer PowerPoint (a) Morphology of shoot of Cassiope tetragona collected May 26, 2007, Longyeardalen. Removal of the front row of leaves shows four leaf pairs of the 2006 summer, the leaf primordium for the 2007 growing season and the stem length increase summer 2006. (b) Wintermarksepta, darker colored than the pith tissue, indicating the winterperiod in a longitudinal section of an air‐dried shoot collected August 26, 2006, Longyeardalen.     

The proto-oncogene Ret is required for male foetal germ cell survival

The spermatogenic and oogenic lineages originate from bipotential primordial germ cells in response to signalling in the foetal testis or ovary, respectively. The signals required for male germ cell commitment and their entry into mitotic arrest remain largely unknown. Recent data show that the ligand GDNF is up regulated in the foetal testis indicating that it may be involved in male germ cell development. In this study genetic analysis of GDNF-RET signalling shows that RET is required for germ cell survival. Affected germ cells in Ret-/- mice lose expression of key germ cell markers, abnormally express cell cycle markers and undergo apoptosis. Surprisingly, a similar phenotype was not detected in Gdnf-/- mice indicating that either redundancy with a Gdnf related gene might compensate for its loss, or that RET operates in a GDNF independent manner in mouse foetal germ cells. Either way, this study identifies the proto-oncogene RET as a novel component of the foetal male germ cell development pathway.     

Patterns of motor recruitment can be determined using surface EMG

Previous studies have reported how different populations of motor units (MUs) can be recruited during dynamic and locomotor tasks. It was hypothesised that the higher-threshold units would contribute higher-frequency components to the sEMG spectra due to their faster conduction velocities, and thus recruitment patterns that increase the proportion of high-threshold units active would lead to higher-frequency elements in the sEMG spectra. This idea was tested by using a model of varying recruitment coupled to a three-layer volume conductor model to generate a series of sEMG signals. The recruitment varied from (A) orderly recruitment where the lowest-threshold MUs were initially activated and higher-threshold MUs were sequentially recruited as the contraction progressed, (B) a recurrent inhibition model that started with orderly recruitment, but as the higher-threshold units were activated they inhibited the lower-threshold MUs (C) nine models with intermediate properties that were graded between these two extremes. The sEMG was processed using wavelet analysis and the spectral properties quantified by their mean frequency, and an angle θ that was determined from the principal components of the spectra. Recruitment strategies that resulted in a greater proportion of faster MUs being active had a significantly lower θ and higher mean frequency.     

Sub-Surface Drip Irrigation in Associated with H₂O₂ Improved the Productivity of Maize under Clay-Rich Soil of Adana,Turkey

Maize being sub-tropical crop is sensitive to water deficit during the early growth stages; particularly clay-rich soil, due to the compaction of the soil. It is well-documented that potential sub-surface drip irrigation (SDI) (Full irrigation; SDIFull (100% field capacity (FC)), Deficit irrigation; SDIDeficit (70% FC)) improves water use efficiency, which leads to increased crop productivity; since it has a constraint that SDI excludes soil air around the root-zone during irrigation events, which alter the root function and crop performance. Additionally, in clayrich soils, the root system of plants generally suffers the limitation of oxygen, particularly the temporal hypoxia, and occasionally from root anoxia; while SDI system accomplishes with the aerating stream of irrigation in the rhizosphere could provide oxygen root environment. The oxygen can be introduced into the irrigation stream of SDI through two ways: the venturi principle, or by using solutions of hydrogen peroxide through the air injection system. Therefore, the application of hydrogen peroxide (H₂O₂; HP) can mitigate the adverse effect of soil compactness and also lead to improving the growth, yield and yield attributes of maize in clay-rich soil. Considering the burning issue, a field study was conducted in consecutive two seasons of 2017 and 2018; where hybrid maize was cultivated as a second crop, to evaluate the effect of liquid-injection of H₂O₂ (HP) into the irrigation stream of SDI on the performance of maize in a clay-rich soil field of Adana, Turkey. When soil water content decreased in 50% of available water, irrigation was performed. The amount of water applied to reach the soil water content to the field capacity is SDIFull (100% FC) and 70% FC of this water is SDIDeficit (70% FC). In the irrigation program, hydrogen peroxide (HP) was applied at intervals of 7 days on average according to available water with and without HP: SDIFull (100% FC) + 0 ppm HP with full SDI irrigation; SDIFull (100% FC) + 250 ppm HP with deficit SDI irrigation; SDIDeficit (70% FC) + 0 ppm HP, SDIDeficit (70% FC) + 250 ppm HP and SDIDeficit (70% FC) + 500 ppm HP. Deficit irrigation (SDIDeficit (70% FC)) program was started from tasseling stage and continued up to the physiological maturity stage with sub-soil drip irrigation. H₂O₂ was applied 3 times during the growing season. Two years’ results revealed that the liquid-injection of H₂O₂ into the irrigation stream of SDI improved the growth and yield-related attributes and grain yield of maize. Based on the obtained results, during the extreme climatic condition in the year 2017, SDIFull (100% FC) + 250 ppm HP was more effective than SDIFull (100% FC) + 0 ppm HP on all traits for relative to full irrigation. While, during the favourable climatic condition in the 2018 season, SDIFull (100% FC) + 250 ppm HP was more effective than full irrigation with SDIFull (100% FC) + 0 ppm HP for the grain yield, grains, and SPAD value. Accordingly, the most effective treatment was SDIFull (100% FC) + 250 ppm HP, as it gave the highest growth and yield-related attributes and grain yield of maize followed by SDIDeficit (70% FC) + 250 ppm HP. Therefore, SDIFull with 250 ppm H₂O₂ using as liquid-injection may be recommended to mitigate the adverse effect of soil compactness particularly water-deficit stress in clay-rich soil for the sustainability of maize production.     

Amide 1 Expression in Psoriasis and Lichen Planus using Synchrotron Infrared Microspectroscopy

Psoriasis vulgaris and, Lichen planus are cutaneous inflammatory conditions that usually exhibit distinctive morphology. Ten psoriasis vulgaris and, ten Lichen planus patients (mean age, 45 ± 10.27 years) with confirmed histopathological diagnoses were analyzed. In the current study synchrotron infrared (IR) microspectroscopy was used to differentiate between these two conditions based on their lymphocytic proteins analyses. It was found that β-sheets protein structure, known to represent cell apoptosis, were expressed significantly in Lichen planus conditions than that of the psoriasis vulgaris when analyzed against the established normal control groups of five patients of comparable age and, genders (P = 0.001, 0.03 respectively). Also, the amide 1 protein type within the epidermis of Lichen planus were expressed in significant proportions as compared to psoriasis vulgaris (P < 0.001). On the contrary, the amide 1 protein structural types were found clustered in psoriasis vulgaris in different IR spectra than that in Lichen planus as observed in a number of patients during this study. These observations indicated that the concentration of amide 1 protein in psoriasis vulgaris varies to that of Lichen planus. In conclusion, both psoriasis vulgaris and, Lichen planus have different types of epidermal and, dermal protein structures and, this information can be of clinical diagnostic and therapeutic use for these cutaneous inflammatory conditions in near future.     

A biomolecular isolation framework for eco-systems biology

Mixed microbial communities are complex, dynamic and heterogeneous. It is therefore essential that biomolecular fractions obtained for high-throughput omic analyses are representative of single samples to facilitate meaningful data integration, analysis and modeling. We have developed a new methodological framework for the reproducible isolation of high-quality genomic DNA, large and small RNA, proteins, and polar and non-polar metabolites from single unique mixed microbial community samples. The methodology is based around reproducible cryogenic sample preservation and cell lysis. Metabolites are extracted first using organic solvents, followed by the sequential isolation of nucleic acids and proteins using chromatographic spin columns. The methodology was validated by comparison to traditional dedicated and simultaneous biomolecular isolation methods. To prove the broad applicability of the methodology, we applied it to microbial consortia of biotechnological, environmental and biomedical research interest. The developed methodological framework lays the foundation for standardized molecular eco-systematic studies on a range of different microbial communities in the future.     

Simply the best: the transition of savanna saplings to trees

Tree cover in savannas is determined as much by disturbances from fire and herbivory as by rainfall and soil resources. Fire especially acts to limit tree cover via a demographic bottleneck, limiting the recruitment of tree saplings to adults. Because sapling growth rates determine rates of sapling to tree recruitment, predicting changes in tree cover requires data on sapling growth rates, commonly expressed as population means. Here, we discuss the variability in sapling growth rates in Acacia populations in a savanna in Hluhluwe iMfolozi Park in South Africa. Saplings growing at mean rates under typical fire regimes in African savannas would likely never escape the fire‐trap to become adults. Only the fastest growing saplings could grow above the flame zone between fires. We suggest that maximum growth rates are more ecologically relevant than mean growth rates in natural populations and experiments. Maximum growth rates are better than mean growth rates as predictors of sapling release within species, as shown here, and probably of which species are likely ‘winners’ in savanna tree communities.